1. Field of the Invention
The present invention generally relates to lighting devices. More particularly, the present invention relates to ornamental lighting devices which display illuminating arcs of plasma.
2. Description of the Related Art
Several display lamps are known in the art which display arcs of plasma from an electrical discharge, sometimes imitating lightning. These display lamps typically have a nonconductive shell containing specific ionizable gases, such as neon (Ne), argon (Ar), krypton (Kr), helium (He), and xenon (Xe), and one or more electrodes disposed in the inert atmosphere. High voltage electricity is the directed to the electrodes to specifically cause arcs of plasma in the inert atmosphere. Several designs utilize either spherically shaped sealed envelopes or cylindrical sealed envelopes to hold the inert gases captive. In some instances, the intensity and location of a specific plasma arc discharge in the plasma display lamp can be altered with the proximity of a conductive body such as a person's hand.
U.S. Pat. No. 4,956,579 and U.S. Pat. No. Des. 326,574 disclose a plasma display having a double-walled disclosure. The plasma display includes a gas-containing envelope that forms a cylinder and an electrode is disposed on the sealed envelope to cause plasma arcs therein upon the supply of a constant alternating current (AC) signal from an AC adapter to the electrode. The '579 patent does not disclose a specific composition of ionizable gas for use in the envelope or the use of voltage and frequency manipulation to cause changes in the plasma arcs, and their interrelation.
U.S. Pat. No. 4,754,199 discloses a self-contained gas discharge display device that includes a single electrode in a discharge chamber comprised of the upper portion of a dome. The device of this patent particularly includes a shield means to establish discharge-supporting electric fields in the discharge chamber, the shield being located between the base and the discharge chamber.
U.S. Pat. No. 4,379,253 discloses an ornamental discharge lamp and is particularly directed towards the power supply of the lamp. The lamp includes one or more electrodes in a light-transmitting envelope containing an ionizable fluid. The ornamental lamp uses an oscillator and by modifying the oscillator voltage to the electrode(s) in the lamp, changing the position of the electrodes, and changing the discharging gas, effects changes in the discharge designs and colors. The voltage disclosed for transmission to the electrode(s) is 10,000 volts or higher.
U.S. Pat. No. 5,281,898 discloses a display device which has a double-walled envelope with a plurality of electrodes therein. The plurality of electrodes receive an AC high voltage current (up to 15,000 volts) to cause a discharge between the electrodes in the envelope. The cycling of the alternating current (120 hz) causes re-ionization of the discharging gas and establishes a new plasma arc from one electrode to the other to cause a "flickering display."